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quadrajet idle tubes

19K views 13 replies 5 participants last post by  cobalt327 
#1 ·
i called my local carb shop and they said my issue for the qjet wasnt the metering rod but the idle tubes, he was telling me theres a certain " sound " they make when u blow air through them.

he offered to blow the tubes for me for free and if they were clogged he'd tell me, but the way he talked to me on the phone i was kinda hoping to never meet him.


i pulled mine out ( they looked somewhat tampered with or like if someone scratched the surface of one ) and after looking up replacement tubes i see that they are .035 tubes.

Idle Pickup Tubes - Rochester Quadrajet Carburetor Parts


mine i can slip a .039 bit in the stepped end and a .052 bit inside the opened end ( what u see in the carb base>under what u put the drywall screw in to remove them)

someone mentioned that theres .037 tubes but idk


so can anyone explain what i have versus what i now need being i removed them and need new ones ?

id prefer not to meet this gentleman lol
 
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#2 ·
I got the most complete Quadrajet Rebuild kit I could from Cliff Ruggles, and it just replaced my stock idle tubes. From what I recall. the key point in his book was to make sure the tubes are not plugged. I don't remember much discussion about using a different sized tube.

I don't have Ruggles's book handy, but can try to find my copy if you don't get any better answers to your question.

Bruce
 
#4 ·
did the book talk about cleaning those ports where the tubes came out of ?

the guy i talked to said ( just because air and carb cleaner goes through the idle tubes that doesnt mean theyre cleared out, they become "corrosantifyed" and plugged up)

also how did u install the new tubes ???
 
#7 ·
According to Ruggles' book, "the restriction in the idle tubes varies greatly in different applications", so size does matter. However, it is also matched to the other idle passages, so just changing to larger tubes may not be a good idea.

The trapped dirt is under the idle tubes, so once you get them out it should be easy to clean out the area. You can also use a stiff wire to break loose any gunk that is trapped at the bottom.

If you got the tubes out, that is the hard part. You have to use a small drill bit or punch to drive the idle tube down, and then use a drywall screw to engage the outer collar and pull it out. Once the collar is out, the tube should just drop out when you turn the carb over.

To put in the new tubes I just pushed the tube and collar as far down as it would go, and then used a small piece of wood to drive it down until it was level with the carb. Take it slow, because you want the tube straight and you don't want to flare the top end by hitting it too hard.

Bruce
 
#8 ·
wow thankyou !



thankyou for the details! since i was stupid and pulled the tubes while i had the carb apart to make throttleshaft bushings, for all i know it was the throttle shaft all along, and i really think that since i see no grime/grit/$h!t down where those tubes were. after making my bushings i cant believe how the shaft doesnt wobble, so im going to believe that the 1/16 slop in the throttle shaft was like leaving the vac advance unplugged =[
 
#10 ·
Have to agree, Cliff Ruggles is the man you want to talk to about your Q-Jet. Cliff's High Performance, Mt. Vernon, Ohio.

His kits include the tubes. He knows which carbs need the larger ones (emmissions related). Not cheap, but absolutely the most complete "kit" available. He and I disagree on floats, though. I prefer brass, as "Qaudra-Flood" is an earned nickname, based on "heavy" fiber floats. Many a rebuilt Q-Jet has been scrapped because it still would "flood" after the rebuild, when a new float would have cured it. Brass floats don't get "heavy" unless they leak. Borg Warner, NAPA and many others still offer brass for most carb numbers.

Though more "Pontiac-related", his book is among the most comprehensive studies of Q-Jet. Cliff is a Pontiac guy, and is responsible for the carbs on some of the quickest NHRA SS Pontiacs including the Angeles car (9.0s '68 Firebird, C/SS/A). Virtually everything applies to all Q-Jets, regardless of original brand. SA Designs is the publisher.

Jim
 
#12 ·
My rebuild kit came with a standard replacement set of idle tubes like you have in the picture. I also asked them to include mixture screws that had a standard screw head instead of the D-shaped head on my original screws.

Its still hard to get to my idle screws because they originally had anti-tamper caps over them. The previous owner ground the caps off, but the screws are still back under the overhang of the carb flange. The screwdriver has to be almost exactly horizontal to reach the screws, and its hard to see the screw heads. At that angle my hands also get close to the fan and shroud.

Bruce
 
#14 ·
well i have a new set on the way along with the mixture screws. i dont have too hard of a time with turning them but it is a pain too, something about my hands and flex fans just dont get along =]
If the idle screws have the "double-D" or hex-shaped heads, slot them for a straight blade screwdriver before installing them- OR- get an idle screw adjustment screwdriver w/the different bits that include the Q-jet screw heads. The tool also has the added benefit of a flexible shaft to allow you to keep away from the fan and belts.;)


Double-D screw


Idle mixture adjustment tool
 
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